Re: Making the planner more tolerant of implicit/explicit casts

On Thu, Oct 11, 2012 at 5:59 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> I'm reasonably convinced that this is a good fix for HEAD, but am of two
> minds whether to back-patch it or not. The problem complained of in
> bug #7598 may seem a bit narrow, but the real point is that whether you
> write a cast explicitly or not shouldn't affect planning if the
> semantics are the same. This might well be a significant though
> previously unrecognized performance issue, particularly for people who
> use varchar columns heavily.

I have had a few bad experiences with people getting *really* upset
about plan changes in minor releases, so I would be disinclined to
back-patch this, even if we're fairly sure that it will be an
improvement in most/all cases. It's just not worth the risk of
discovering otherwise.

--
Robert Haas
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